Method of treating coal



Nov. 11, 1969 E. F. NELSON METHOD OF TREATING COAL Filed Jan. 25, 1968 United States Patent O 3,477,941 METHOD F TREATING COAL Edwin F. Nelson, Arlington Heights, Ill., assiguor to Universal Oil Products Company, Des Plaines, lll., a corporation of Delaware Filed Jan. 25, 1968, Ser. No. 700,536 Int. Cl. Cg 1/04 U.S. Cl. 208--8 4 Claims ABSTRACT 0F THE DISCLOSURE A Method for the liquefaction of coal via solvent extraction using a hydrogen-donor selective solvent. The method pulverizes coal in the presence of solvent utilizing high velocity impact means situated in a digestion zone which is maintained under coal liquefying conditions. Preferably, the method includes injecting hydrogen gas into the digestion zone thereby facilitating the conversion of solid coal into liquid coal products. Hydrocarbons useful as fuel and/or chemicals may be obtained from the liquid coal extract.

Background of the invention This invention relates to a coal treating process. It also relates to a method for liquefying coal using a selective solvent. It particularly relates to a method for obtaining valuable liquid hydrocarbons from solid particulate coal utilizing high velocity impact means to crush the coal in the presence of selective solvent and, preferably, hydrogen. v

y It has long been known that hydrocarbon gases, liquids,

pitch and chemicals may be obtained in some form from coal which is mined from the earth. Usually, the prior art has employed destructive distillation or other gasification processes for the conversion of coal into these more valuable and useful products. Recently, the prior art has developed a high pressure hydrogenation of coal technique to eifectuate such conversion. Still more recently, methods involving solvent extraction techniques have been developed for obtaining useful fuels and chemicalsfrom coal whereby the coal is contacted with a selective lsolvent which acts as a hydrogen-donor for supplying sufficient hydrogen to the coal to aid in converting it into a liquid state. Following the solvent extraction step, the prior art schemes have generally utilized various recovery procedures, such as hydrogenation of the liquid coal extract, for increasing its value and utility together with retorting or coking of the residual materials obtained from the solvent extraction step to still further convert these coal derived products into more valuable products. However, none of the aforementioned prior art proceduces have been commercially eilicient or feasible to warrant widespread commercial exploitation of converting coal into liquid products. Generally, the deficiencies in the prior art schemes have not only involved capital investment problems and disposal problems of the residue or waste frequently having high metals content, but also involved liquid product quality and quantity problems which have yet to be solved in an economical and facile manner.

Since it is clear to those skilled in the art that the vast mineral reserves of bituminous coal represent an extremely important supply of energy, it would be desirable to improve upon the prior art techniques, particularly the solvent extraction technique in order to rep duce the cost of obtaining yhigh quality petroleum-type products from coal. Accordingly, the present invention provides an improved process for the conversion of solid coal into liquefied products utilizing the solvent extraction technique.

3,4|77,941 Patented Nov. 11, 1969 Summary of the invention Therefore, it is an object of this invention to provide a process for treating coal.

It is also an object to provide a process for the liquefaction of coal whereby valuable liquid hydrocarbons are obtained therefrom.

It is a specific object of this invention to provide an improved process for treating coal which involves the impact pulverization of coal while simultaneously converting the pulverized coal to liquid coal products with a selective solvent.

Thus, in accordance with the practice of the present invention, there is provided a method for the 1iquefactionvof coal which comprises admixing solid particulate coal with solvent in an eduction device, propelling said admixture against impact means under conditions suicient to fracture said coal into smaller size particles, subjecting the smaller size coal resulting from said impact means to `coal liquefying conditions in a digestion zone and removing from said zone liqueedcoal.

Another embodiment of this invention includes the method hereinabove wherein said fracture conditions include the injection of hydrogen gas into said eduction device thereby becoming part of said admixture.

Still another embodiment of this invention includes the broad method hereinabove wherein saidl liquefying conditions include surrounding said impact means with said solvent in liquid phase. In other words, for this embodiment, the impact means is physically located inside the digestion vessel which operates substantially liquid-full with the selective solvent chosen for the coal.

It can be seen from the description of the invention presented thus far that the essence of the invention embodies the use of impact pulverization means in the presence of the selective solvent for the liquefaction of coal. Additionally, the preferred embodiments include the presence of hydrogen gas in the digestion zone to aid in the conversion of solid particulate coal to liquefied coal products. It is believed that the introduction of the lean solvent in this unique fashion results in improved contact between the solvent and the coal while providing a continuous manner of converting solid coal into liquefied products in a more facile and economical manner.

In brief, the operation of the present invention involves the introduction of coal and solvent into an eductor device which is constructed in a manner to propel the admixture through nozzle means against an impact plate with suflicient velocity to fracture the small coal into smaller particles. Preferably, the impact means is physically located inside a digestion vessel which is maintained under coal dissolving conditions including having present liquid solvent which substantially surrounds the impact means. A suitable residence time is maintained in the digestion zone by utilizing the technique of hindered settling whereby the upward velocity of coal and solvent is adjusted lso that substantially all of the coal is converted to liquid products prior to being withdrawn from the digestion zone. The hindered settling technique is accomplished by having the impact means located in the lower end of a vertically disposed digestion zone Iand withdrawing the resulting liquid coal extract and solvent from the upper end thereof. At the same time, operating in this -manner provides a means for settling out of solution the ash and other undissolved materials which mayl be removed from the digestion zone at the bottom thereof.

In the preferred manner of operation there is introduced into the eduction device hydrogen gas which not only acts -as a carrying medium for the solvent and coal, but also aids in the conversion of solid coal to liquid coal extract while simultaneously at least partially hydrogenatingthe solvent present in the digestion zone. In this manner, the solvent is maintained in a desirably high hydrogen content state. The use of the hydrogen gas can be further enhanced by introducing into the digestion zone a suitable hydrogenation catalyst which, preferably, would be introduced into the upper end of the digestion zone.

It is believed that one `of the reasons the practice of the preferred embodiment of the invention produces -such desirable results is the manner in which hydrogen balance is maintained in the system. For example, during the digestion operation it is believed that hydrogen is transferred from the solvent to the coal thereby aiding in the conversion of the coal into a liquid product. Thus, the solvent, in effect, becomes reduced in hydrogen content. Preferably, therefore, hydrogen gas is introduced into the digestion zone in order to restore the hydrogen content of the solvent to its original hydrogen content. In other words, in the broad embodiment of the invention, as the solvent passes upwardly through the solvent digestion zone, it becomes more and more depleted in hydrogen content as it contacts the crushed coal passing downwardly through the zone. While unique advantages ywere found in this manner of operation over the prior art schemes, it was also discovered that the inventive method could be further improved by having the digestion take place in the presence of -a hydrogen gas in such a manner that the solvent substantially throughout the digestion zone is maintained, in effect, in its highest hydrogen content thereby significantly increasing the efficiency of the coal conversion reaction.

By operating in this preferred manner and in some cases utilizing hydrogenation catalyst in the digestion zone, one of the ultimately recovered hydrocarbon products is now imminently suitable for recycle to the pulverization zone since its hydrogen content has been restored substantially to its prior ilevel.

The coal preferred for use in the practice of the present inventive process is of the bituminous type, such as Pittsburgh seam coal. More preferably, however, the bituminous coal is a high volatile content coal having a solids content greater than about 2O weight percent of M.A.F. coal (moisture and ash-free coal). Although the inventive method will be described with reference to the treating of bituminous coa-l, it is within the concept of the present invention to apply the inventive process to a sub-bituminous coal, lignite, and other solid carbonaceous materials of natural origin.

The coal feed utilized in the present invention may be introduced into the eduction device in its substantially dry state through lock hopper means, screw conveyor means, or other means available to those skilled in the art. The solvent and particulate coal may be introduced into the eduction device as separate streams or may be admixed prior to introduction into the eductor device. As used herein, the phrase admixing solid particulate coal with solvent or words of similar import are intended to embody all means and combinations of causing contact between relatively large diameter coal particles, solvent, and in some cases, hydnogen gas. The formation of this admixture is not critical to the practice of this invention. On the other hand, however, it is essential that coal, solvent and -where appropriate, hydrogen gas, be passed through the eduction device in such a manner that these components are propelled against the impact means with suflcient velocity to cause substantial fracture of the coal into relatively small diameter coal particles.

With respect to the benefit gained from having the solvent present at the point of impact, it is believed that at the point of shear for the fracturing of the coal particles, the shear site is extremely reactive and, therefore, hydrogen can be transferred into that site more easily than if the coal is pulverized prior to contact with the solvent. In addition, the smaller particles of coal which are sheared away from a relatively large lump immediately exposes not only the highly reactive shear site to the solvent, but also exposes an extremely large surface area to the solvent thereby enabling the resulting small particles of coal to almost immediately dissolve in the solvent which is surrounding the impact means and become part of the liquid coal extract.

Additionally, there has been some discussion in the prior art that the presence of oxygen or oxygen compounds on the surface of the coal makes it difficult for the coal to react properly with the suitable solvents for the conversion thereof into liquid coal extract. It is further believed, therefore, that by pulverizing or by crushing the coal in the presence of a liquid solvent, oxygen compounds or the presence of oxygen have been excluded from the highly reactive shear sites along the coal, thereby further enabling the transfer of the hydrogen from the solvent to the coal to become of significantly increased efficiency.

Extraction of coal by means of a selective solvent is, by definition, a partial conversion of the coal since not only is the coal reacted with the hydrogen which is transferred from the solvent, but is, in the preferred embodiment, also reacted with the hydrogen which is added during the extraction operation. In addition, there is a solution phenomenon which actually dissolves the coal which has accepted the hydrogen into the solvent. Therefore, as used herein, the terms liquid coal extract and liquefied coal fraction or dissolved coal or other words of similar import are intended to include the liquid product which is obtained by treating the coal with a selective solvent and, generally, will be described on the basis of being solvent-free even though a portion of the liquid coal extract comprises hydrocarbons suitable for use as the selective solvent.

The practice of the present invention is preferably performed under conditions which increase the kinetics of the reaction while maintaining the components therein primarily or substantially in liquid phase; although, in some cases it may be desirable to practice this invention in the presence of vaporized solvent by using a vapor-fluid extraction technique.

Suitable solvents for use in the practice of this invention are those which are of the hydrogen-donor type and are at least partially hydrogenated and include naphthalenic hydrocarbons. Preferably, the solvent is one which is in liquid phase at the recommended temperature and pressure for the digestion and/or pulverization step. Mixtures of hydrocarbons are generally employed and, preferably, are derived from intermediate or final products obtained from subsequent processing following the practice of this invention. Typically, these solvent hydrocarbons or mixtures of hydrocarbons boil between about 260 C. and 425 C. Examples of suitable solvents are tetrahydronaphthalene (Tetralin), Decalin, biphenyl, methylnaphthalene, dimethylnaphthalene, etc. Other types of solvents which may be added to the preferred solvents of this invention for special reasons include phenolic compounds such as phenols, cresols, and xylenols. It is also to be recognized that in some cases it may be desirable during a subsequent separation step prior to the removal of the solvent from the liquid coal extract to add an anti-solvent, such as saturated parainic hydrocarbon like hexane, to aid in the precipitation of any tarry and solid residue carried over into the coal extract of the invention.

However, in the selection of a suitable solvent it must be recognized that the solvent must have the ability to transfer hydrogen to the pulverized coal during the extract step. In other words, in the broad embodiment of this invention (eg. no added hydrogen), it is a requirement of this invention that the rich solvent leaving the digestion zone having coal dissolved therein has a reduced hydrogen content compared to the hydrogen content of the lean solvent which is added to the pulverization zone in admixture with the feed. It has also been explained that another critical feature of the preferred embodiment of the invention is the selective hydrogenation of the solvent during extraction in order to increase its hydrogen content so that hydrogen may be more easily transferred from the solvent to the coal.

One of the convenient ways of optimizing the specific hydrotreating operation during extraction is to use the Ifactor analysis for determining the degree to which hydrogen has been added to the hydrogenation reaction zone feed. This analytical technique permits the characterization of various types of aromatics in a hydrocarbon mixture by means of the I-factor analysis. The technique utilizes mass spectrometer analysis employing a low ionizing voltage. The ionizing voltage is chosen such that only those hydrocarbons to be characterized are ionized while other hydrocarbon types are not ionized under the potential chosen. For example, since compounds more saturated than aromatic hydrocarbons, such as the parafn hydrocarbons, have an ionization level above volts, the ionization chamber is thus maintained at a potential of about 7 volts so that only the aromatic hydrocarbons are ionized and the saturated compounds will not be Observed on the mass spectrum. As those skilledin the analytical art know, the mass spectrum reveals molecular ion peaks which correspond to the molecular weight of the aromatic compound. Thus, the technique permits characterization of the aromatic hydrocarbons by means of the general formula CnH2n J where J is the herein rcferred to J-factor for the practice of the present invention. The following table shows the relationship between the J-factor and the type of aromatic.

Lfactor No.: Type of aromatic hydrocarbon 6 Alkyl benzenes and benzene. 8 lndanes, Tetralins. 10 Indenes. 12 Alkyl naphthalenes and naphthalene. 14 Acenaphthenes, tetrahydroanthracene. 16 Acenaphthalenes, dihydroanthracenes. 18 Anthracenes, phenanthrenes.

Using this J-factor analysis in characterizing the degree of hydrogenation during extraction allows for the optimum treatment of said solvent to produce a high quality hydrogen enriched solvent for use in converting coal into liquid coal extract. The J-factor analysis is simply a convenient means for optimizing the hydrogenation technique in the practice of the preferred embodiment of the present invention.

The operating conditions maintained in the digestion zone may be varied widely. The temperature, for example, may be varied essentially from atmospheric temperature to a relatively high temperature. It is distinctly preferred in the practice of this invention that the temperature of the coal and the solvent be -maintained at a relatively high level, say, from 300 C. to 500 C. The pressure in similar manner may be varied over an extremely wide range; for example, from atmospheric pressure to, say 10,000 p.s.i.g. with a preferred pressure being about 500 p.s.i.g. In all cases it is distinctly preferred that the operating conditions be chosen so as to maintain the solvent and dissolved coal in substantially liquid phase. These conditions should also be chosen so as to maintain the digestion zone substantially liquid-full; at least over the volume of the digestion zone where the major portion of the dissolving action takes place. The amount of solvent which is used in the present invention should be from 0.2 to 10 pounds of solvent per pound of solid coal entering the digestion zone. Satisfactory results may be obtained in utilizing approximately equal amounts of solvent to coal on a weight basis.

As previously mentioned the upwardly flowing solvent in the digestion zone, and, preferably, the upwardly flowing hydrogen gas provided a residence time for the solid coal to be in contact with the solvent through the hindered settling technique. Generally, a residence time from 30 seconds to 5 hours is suicient and, preferably, the amount of hydrogengas introduced into the system is sucient to aid in dissolving the coal and to substantially maintain the hydrogen content of the lsolvent at substantially the level of the lean solvent. In `all cases, the

combination of operating conditions should be sufficient so that a total in excess of 50% lby weight and, typically, from 70 to 90% by weight of the M.A.F. coal has been liquefied. The amount of hydrogen gas necessary to perform this function may range from 1,000to 100,000 standard cubic feet per barrel of lean solvent entering the system. Typically, however, the amount of hydrogen added to the digestion zone in the preferred embodiment will be in the range from 2,000 to 10,000 standard cubic feet per barrel. However, the amount of hydrogen entering the digestion zone should not be in excess of that which would cause foaming or carry-over of solid coal out of the upper end of the digestion zone. Those skilled in the art familiar with the teachings presented herein and general knowledge will understand howto control the amount of hydrogen in conformity with the J -factor analysis on the solvent leaving the digestion zone and on other design parameters.

While the purpose of the digestion zone, including the preferred embodiment of adding hydrogen to the digestion zone, is to substantially complete the conversion of the coal into a liquid coal extract, it may also be desirable to add to the digestion zone a hydrogenation catalyst. The catalyst used may @be conventional, may be homogenous or heterogenous and may be introduced in the pulverization zone and/or digestion zone in admixture with the liquid solvent or with the solid coal.. Those skilled in the art, from a knowledge of the characteristics of the coal, solvent, and the properties desired for the end product will know whether or not it may be desirable to use any or all of these desirable features in the digestion zone. Conventional solid particulate (preferably, finely divided) hydrogenation catalyst may be desirable, such as palladium on an alumina support or a cobalt-molybdate catalyst or any other hydrogenation catalyst known to those skilled in the art and applicable to the solvent-coal -system environment maintained in the digestion zone.

Hydrogenation in the digestion zone generally accomplishes the following functions: transfer of hydrogen directly to coal moelcules; transfer of hydrogen to hydrogen donor molecules; transfer of hydrogen from hydrogen donor molecules to coal molecules; and, combinations of the above. Homogenou's catalysts may be introduced with the coal, or hydrogen donor compounds, in the pulverization step prior to the digestion zone. Examples of catalysts suitable include compounds containing tin, nickel, molybdenum, tungsten, and cobalt.

Following the digestion zone, the solvent containing dissolved oil is passed into a separation zone for the recovery therefrom of valuable hydrocarbon products. Typically the'se products are normal gasoline boiling range products and/or chemicals, aromatic hydrocarbon-containing fractions, heavy fuel oil fractions, and the like, the utility of which is well known to those skilled in the art. As previously mentioned, at least a portion of the coal extract is suitable for use as a coal solvent and may, therefore, be recycled at least in part to the solvent digestion zone as lean solvent therein.

The construction of the impact means may be from any design available to those skilled in the art. Generally, it should be so constructed so that the extremely high velocities of coal and solvent will cause the substantial fracture of .the coal upon impact with the means. The material of construction used for this device may be from any relatively hard material, such as tungsten carbide, stainless steel, alloys of various other types, etc. The only criteria for the material of construction would be that the impact means should not, to any considerable extent, Ibe eroded by the i-mpaction of coal particles on its surface. Desirably, the impact device would be a flat plate constructed a relatively short distance from the end of the nozzle which is being fed with the solvent and coal. Other shapes can, of course, be used, such a curved surface to direct the crushed coal particles into desired areas of the digestion zone. Other geometric patterns for construction of -the impact device can be utilized to influence the flow of solvent and/or solid material within the digestion zone in any manner conceived by those skilled in the art. In addition, the location of the impact means may ybe either within the digestion zone or immediately outside of the digestion zone. It is distinctly preferred in the practice of this invention that the impact device be physically located within the digestion zone so that simultaneous liquefaction of the pulverized coal particles may occur.

As used herein, the eduction device preferably comprises a fluid eductor means. By definition, the fluid eductor means will include ejectors and injectors of the jet pumptype commonly known to chemical engineers. The words ejector and eductor are used interchangeably herein. As is well known, these devices generally include a Venturi nozzle which causes ya tremendous increase in the speed of the materials owing through it. In essence, therefore, the term eduction device broadly encompasses any device for significantly increasing the velocity of the solvent and coal to an extent such that the coal willv fracture upon impact with the impact means previ ously.described hereinabove. In the practice of the preferred embodiment of the invention the impact conditions are chosen so that the relatively large diameter coal particles are reduced in size to at least a -8 Tyler screen size and under the further conditions that the solvent has a chance to react and dissolve the coal particles substantially simultaneously as the large coal particle is fractured. The primary requirement for handling coal in the practice of this invention is that the relatively large diameter coal, usually having an average diameter in excess of 0.08 inch and, typically, about 0.25 to 1.0 inch, is lpropelled through the eduction device with sufficient velocity such that on impact the coal particles will reduce in size to an average particle diameter which would be of at least -8 Tyler screen size and, preferably, would be reduced to an average particle diameter of 14 Tyler screen size. As used herein, the term Tyler screen refers in all instances to the commercial Tyler Standard Screens. A correlation between Tyler screen mesh and average particle diameter is as follows:

Average diameter of Tyler screen mesh: particles Dvg in.

The invention may be more fully understood with reference to the appended drawing which is a schematic represent-ation of apparatus for practicing one embodiment of the present invention.

Description of the drawing Referring now to the drawing, relatively large diameter solid particulate coal having an average particle diameter in excess of 0.08 inch is introduced in a substantially dry condition into the system from hopper 10. Typically, the temperature of the dry coal is about 300 F. Simultaneously, hot selective solvent enriched in hydrogen content is introduced at a temperature of about 750 F. into admixture with the coarse coal via line 11 into eductor 12. Preferably, hot hydrogen also is introduced into eductor 12 at a typical temperature of about 900 F. The entire eliiuent from eductor 12 passes via conduit 14 which is an appropriate nozzle device into digester vessel 16 at an extremely high velocity and/or pressure. This eluent comprising solvent, coal particles, and hydrogen is propelled against impact means 15 which is a at plate composed of tungsten carbide. As the solid coal particles irnpinge 'against plate 15, the particles are fractured into smaller sized particles which are scattered in random pattern throughout the solvent which is contained in digester 16 and which substantially surrounds impact device 15. In other words, digester 16 is liquidfull of the selective solvent, at least over that portion of digester 16 through which coal is liquefied.

As the method continues, the coal particles and solvent pass in an upward fashion through digester 16 at a rate which results in the hindered settling of the solid particles thereby providing sufficient residence time for at least a total of 50 weight percent of the M.A.F. coal to be converted into liquid coal extract. The solid particles which eventually settle in digest/er 16 are removed via line 17 and a portion thereof is rejected via line 20 with the remainder passing via line 21 back into eductor 12 for another passage through the impact device. Not shown are optional separation means for the selective recovery of undissolved coal particles which may then be recycled to the eductor as previously described. A liquid coal extract stream containing dissolved coal and solvent is removed from digester 16 at the upper end thereof via line 18. Desirably, a vapor space is maintained at point 30 in digester 16 which provides separation means for unreacted hydrogen gas to be recovered and retuned via line 19 to the eductor device 12.

Additional hydogen gas, if needed, may be introduced into the system via line 22 and added solvent, if needed 0r desired, may be introduced into the system via line 23.

Referring now to the liquid coal extract stream in line 18, this material is passed into fractionator 24 which may be a conventional distillation column type. Suitable conditions are maintained therein such that a distillate fraction comprising light hydrocarbons may be withdrawn via line 26 and a liquid coal extract stream may be removed via line 25 from the bottom of fractionator 24 for further processing in accordance with the practices known to those skilled in the art including processing for upgrading and/ or for separating the liquid coal extract to the desirable valuable product of motor fuel and/ or chemicals.

In the practice of the present invention, a material suitable in boiling range as solvent for the coal is withdrawn from fractionator 24 via line 27 and withdrawn from the system for other uses known to those skilled in the art, or in the preferred embodiment of this invention, at least a portion thereof is returned to eductor 12 via lines 28 and 11. Still further, if desired, a portion of the withdrawn material in line 18 may also be returned to eductor 12 via lines 29, 28, and 11, respectively.

It was discovered in the practice of the present invention that the utilization of hydrogen gas in the digester 16 permitted the use of less solvent than would otherwise be required. In addition, the presence of an excess of hydrogen gas and solvent at the point of fracturing the coal particles provided a means for a more eiiicient conversion of the solid coal into liquid coal products.

Preferred embodiment From the discussion presented hereinabove, the preferred embodiment of the present invention includes a method for treating coal which comprises: (a) admixing particulate coal of relatively large diameter with solvent and passing said admixture into a hydrogen gas stream in an eduction device; (b) propelling said admixture and hydrogen against impact means located in the lower end of a vertically disposed digestion zone containing liquid solvent under pulverization conditions suicient to convert said large diameter coal into relatively small diameter coal; (c) passing said relatively small diameter coal and hydrogen through said liquid solvent in the digestion zone in an upwardly iiowing manner under contions sufficient to substantially liquefy said particulate coal; (d) withdrawing from the upper end of said zone a stream containing liquefied coal; and, (e) withdrawing from the bottom of said zone a stream containing ash and non-liquid materials.

The invention claimed is: 1

1. Method for treating coal which comprises:

(a) admixing particulate coal of relatively large diameter with solvent and passing said admixtre into a hydrogen gasstream in an eduction device;`

(b) propellingsaid adrnxture and hydrogen against impact means located in the lower end of a vertically disposed digestion zone containing liquid solvent under pulverization conditions sucient to convert said large diameter coal into relatively small diameter coal;

(c) passing said relatively small diameter coal and hydrogen through said liquid solvent in `the digestion zone in an upwardly owing manner under c'nditions suicient to substantially liquefy said particulate coal;

(d) withdrawing from the upper end of said zone a stream containing liqueed coal; and,

(e) withdrawing from the bottom of said zone a stream containing ash and non-liquid materials.

2. Method according to claim 1 wherein hydrocarbon products are separated from the withdrawn stream from the upper end of said zone.

3. Method according to claim 1 wherein said liquefying conditions include superatmospheric pressure, temperature from 300 C. to 500 C., solvent to coal ratio from 0.2 to 10, and a residence time from seconds to 5 hours suilicient to dissolve coal into said solvent such that a total in excess of by weight of said M.A.F. solid particulate coal is liquefied.

4. Method according to claim 3 wherein at least a portion of the solvent Vis selected from the group consisting of tetrahydronaphthalene, decahydronaphthalene, biphenyl, methylnaphthalene, and dimethylnaphthalene.

References Cited UNITED STATES PATENTS 1,940,648 12/1933 Russell 208-8 1,934,023 11/1933 wright 208-10 1,672,231 6/1928 igyan 208-11 3,018,241 1/1962 Gerin 208-8 3,018,242 1/1962 Gerin 208-10 3,075,912 1/1963 Eastman 208-8 1,055,334 3/1913 Laird 208-8 2,379,077 6/1945 `Harding 208-8 1,861,355 5/1932 Owens 208-8 2,681,300 6/1954 kRuidisch 208-8 1,687,763 10/1928 hampton 208-11 DELBERT E. GANTZ,` Primary Examiner V. OKEEFE, Assistant Examiner 

